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EPTC

Publication Date: 9/93

TRADE OR OTHER NAMES

Trade names include Eptam, Eradicane, Eradicane Extra, Shortstop, Genep, Genep Plus-EPTC.

REGULATORY STATUS

Products containing EPTC must bear the signal word "Caution" (1).

INTRODUCTION

EPTC is a selective herbicide used for control of annual grassy weeds, perennial weeds, and some broadleaf weeds in beans, forage legumes, potatoes, corn, and sweet potatoes (1). It is usually applied preemergence, that is before weed seeds germinate, and it is most effective against newly germinated seedlings. EPTC is usually incorporated into the soil immediately after application either mechanically or by overhead irrigation (7). EPTC is available as emulsifiable concentrates and granular formulations (1).

TOXICOLOGICAL EFFECTS

ACUTE TOXICITY

EPTC is moderately toxic by inhalation, dermal absorption and ingestion. Workers subjected to inhalation exposure to EPTC experienced headaches, nausea, general malaise, and impaired working capacity. Animals poisoned in experimental tests displayed excitement, salivation, tearing, spasmodic winking, and depression (2).

EPTC may cause skin irritation and is a strong eye irritant (2, 5). Prolonged contact may cause mild irritation with redness, itching or burning (8).

EPTC is a cholinesterase inhibitor (8). Early symptoms if cholinesterase inhibition are blurred vision, fatigue, headache, vertigo, nausea, pupil contraction, abdominal cramps and diarrhea. Severe inhibition of cholinesterase may cause excessive sweating, tearing, slowed heartbeat, giddiness, slurred speech, confusion, excessive fluid in the lungs, convulsions and coma (2). For more information on cholinesterase, please refer to the Toxicology Information Brief on Cholinesterase-Inhibition.

The amount of a chemical that is lethal to one-half (50%) of experimental animals fed the material is referred to as its acute oral lethal dose fifty, or LD50. The oral LD50 for technical EPTC in rats is 916 to 1,630 mg/kg, 750 to 3,160 mg/kg in mice, 112 mg/kg in cats, and 2,640 mg/kg in rabbits. The dermal LD50 for EPTC in rabbits is 1,460 to approximately 10,000 mg/kg, and 3,200 mg/kg in rats. The TCLO in humans is 135 mg/m3/4-hours inhalation. The inhalation 4-hour LCLO in rats is 200 mg/m3, and 400 mg/m3 in cats (1, 2, 7).

CHRONIC TOXICITY

In a 16 week study of dogs fed 45 mg/kg, effects of brain cholinesterase inhibition and gastric mucosal changes were reported (2). In a 54 week feeding study of EPTC in rats the NOEL was 20 mg/kg/day (5). In a 2-generation study with rats fed 10 or 40 mg/kg, technical EPTC caused degeneration of tissues of the spinal chord, nerves, muscle and heart tissue. No evidence of these effects was seen in a survey of workers who produced and formulated technical EPTC (8).

Reproductive Effects

Mice given dietary doses of up to 24 mg/kg/day on days 6 through 18 of pregnancy did not produce signs of toxicity in pregnant females. When mice were oral doses of 0, 30, 100 or 300 mg/kg/day on days 6 through 15 of pregnancy, maternal mortality and decreased weight gain and food consumption occurred at the highest dose. Decreased fetal body weight and increased loss of fetuses occurred at 100 and 300 mg/kg. No adverse effects on reproduction were observed when rats were fed dietary doses of up to 40 mg/kg for 2 generations (9).

Teratogenic Effects

No teratogenic effects were seen in fetuses of mice given dietary doses of up to 24 mg/kg/day on days 6 through 18 of pregnancy (8). No effects were observed in a teratogenic study in which rats were given 300 mg/kg/day (9).

Mutagenic Effects

Technical eptam was not mutagenic when tested in a series of assays, including assays on microbial and human cell cultures (8).

Carcinogenic Effects

In a 2-year feeding and oncogenicity study of EPTC in mice the NOEL was 20 mg/kg/day and there was no evidence that EPTC causes tumors (5).

Organ Toxicity

In lifetime studies with animals, technical EPTC caused degeneration of tissues of the spinal chord, nerves, muscle and heart tissue. No evidence of these effects was seen in a survey of workers who produced and formulated technical EPTC (8).

Fate in Humans and Animals

When a single oral dose of 0.6 mg was given to rats, 8% was excreted in the urine, 4% in the feces and 85% was expired in the breath. When the dosage was increased to 100 mg, the amount excreted was 36%, 11%, and 38% respectively for each route (6). Expiration of an orally administered material in the breath generally indicates that the material has been absorbed from the gastrointestinal tract and then metabolized by the body. Excretion in the feces would indicate that the material remained in the gastrointestinal tract and was not absorbed into the bloodstream.

ECOLOGICAL EFFECTS

Effects on Birds

EPTC is slightly toxic to relatively non-toxic to birds. The oral LC50 for technical EPTC in bobwhite quail is 20,000 ppm for a 7-day feed treatment (7).

Effects on Aquatic Organisms

EPTC is slightly toxic to fish. The lethal concentration fifty, or LC50, is that concentration of a chemical in air or water that kills half of the experimental animals exposed to it for a set time period. The 96-hour LC50 for EPTC in rainbow trout is 19 mg/l , 27 mg/l in bluegill sunfish, and 17 mg/l in mosquito fish. The 24-hour LC50 in blue crab is greater than 20 mg/l. The 48-hour TLm for technical EPTC in the salt-water inhabiting longnose killifish is greater than 20 mg/l (1, 7).

Effects on Other Animals (Nontarget Species)

EPTC is not toxic to bees if used according to label directions (1).

ENVIRONMENTAL FATE

Breakdown of Chemical in Soil and Groundwater

EPTC is moderately mobile in soil and has a moderate potential to leach into groundwater. It is soluble in water (375 ug/ml), and binds only weakly to soil particles (Koc = 280 g/ml) (4). EPTC binds to dry soils but is readily removed from clay particles by soil water (3). The amount of leaching decreases as clay or organic matter content of the soil increases. In sandy soils in glass columns, EPTC moved to a depth of 9 to 15 inches when 8 inches of water was applied. When the same test was performed on loam and clay soils, the herbicide moved to a depth of only 3 to 7 inches (7).

At recommended application rates, EPTC does not persist in the soil, and should not leave residues that could injure subsequent plantings of sensitive crops. The half-life of EPTC in moist loam soil at 21 to 27 degrees C is approximately 1 week (7). Another source reports a soil half-life of 30 days (1).

Microbial breakdown is the main mechanism by which EPTC is lost from soils. If the soil surface is wet, EPTC must be incorporated into the soil immediately after application to prevent loss into the atmosphere via volatilization (7).

Breakdown of Chemical in Water

Because EPTC is incorporated into the soil upon application, there is little chance that it will enter surface waters (5).

Breakdown of Chemical in Vegetation

EPTC is readily absorbed by the roots of plants and translocated upward to the leaves and stems. EPTC is rapidly metabolized by plants to carbon dioxide and naturally occurring plant constituents (7, 5).

PHYSICAL PROPERTIES AND GUIDELINES

EPTC is a pale to dark yellow liquid with an aromatic odor characteristic of the thiocarbamates. EPTC is hydrolyzed by warm strong acids (1). EPTC is stable under normal temperatures and pressures, but it may pose a slight fire hazard if exposed to heat or flame. Thermal decomposition may release toxic oxides of nitrogen and sulfur (2).

Occupational Exposure Limits:

No occupational exposure limits for EPTC have been established by OSHA, NIOSH or ACGIH (2). ICI Americas, the basic manufacturer of EPTC, limits employee exposure to no more than 0.4 mg/m3 (8).

Physical Properties:

CAS #: 759-94-4
Specific gravity: 0.960 at 25/25 degrees C (7)
H20 solubility: 0.375% at 25 degrees C (1)
Solubility in other solvents: Miscible with common organic solvents such as acetone, ethyl alcohol, kerosene, MIBK and xylene (1, 7)
Boiling point: 127 degrees C at 27 mbar (1); 455 degrees F (235 degrees C) (2)
Flashpoint: 112 degrees C (open cup) (1); for technical EPTC: >200 degrees F or 93.3 degrees C (8).
Vapor pressure: 4.7 mbar at 25 degrees C (1); 34 x 10 to the minus 3 power mm at 25 degrees C (7).
Chemical Class/Use: thiocarbamate herbicide

BASIC MANUFACTURER

Zeneca Ag Products
Wilmington, DE 19897

Review by Basic Manufacturer:

Comments solicited: November, 1992.
Comments received:

REFERENCES

  1. Meister, R.T. (ed.). 1992. Farm Chemicals Handbook '92. Meister Publishing Company, Willoughby, OH.
  2. Occupational Health Services, Inc. 1991 (Feb. 21). MSDS for S- Ethyl Dipropylthiocarbamate. OHS Inc., Secaucus, NJ.
  3. Saltzman, S. and Yaron, B. (ed.). 1986. Pesticides in Soil. Van Nostrand Reinhold Co., NY.
  4. U.S. Department of Agriculture, Soil Conservation Service. 1990 (Nov.). SCS/ARS/CES Pesticide Properties Database: Version 2.0 (Summary). USDA - Soil Conservation Service, Syracuse, NY.
  5. US Environmental Protection Agency. 1983 (Oct. 3). Chemical Fact Sheet for EPTC (Fact Sheet No. 06). Registration Division, US EPA, Washington, DC.
  6. Wagner, S.L. 1983. Clinical Toxicology of Agricultural Chemicals. Noyes Data Corp., Park Ridge, NJ.
  7. WSSA Herbicide Handbook Committee. 1989. Herbicide Handbook of the Weed Science Society of America, 6th Ed. WSSA, Champaign, IL.
  8. ICI Americas Inc. 1992 (Sept. 27). Materials Safety Data Sheet for Eptam Technical. ICI, Wilmington, DE.
  9. Integrated Risk Information System. EPTC. 1990 (Sept. 6). IRIS, Cincinnati, OH.